The present invention relates to a shell, particularly for a ski boot.
The manufacture of boots having overlapping flaps has been widespread for several years.
According to such technology, a significant portion of the surface of the flaps overlaps; after the boot is fastened, the flaps ensure an optimum wraparound effect and watertightness of the boot.
The boots are generally made of plastics and are therefore manufactured by injecting melted material into the mold.
During sports practice, the boot must ensure the structural strength required to correctly control the ski and at the same time ensure that there are no infiltrations of water toward the foot.
These two characteristics greatly influence the manufacture of the boot, because structural strength requires components of considerable thickness and stiffness, while watertightness and comfort require a reduced thickness in order to have a structure which is flexible and can easily shape itself to fit the foot.
During the insertion and extraction of the foot from the boot, the structure must undergo deformation without preventing or hindering the sliding of the foot in the boot; in particular, the two flaps must undergo deformation and slide with respect to each other.
This last action is also affected by the friction generated between the mutually contacting surfaces of the two flaps.
All this usually entails the manufacture of a plastic boot whose characteristics are a compromise and only partially satisfy the above described requirements.
Ski boots with scarcely flexible flaps, which allow limited shaping and afford good retention of the foot but compromise excessively the insertion and extraction of the foot, which are generally difficult and entail forcing, are in fact commonly manufactured.
Moreover, skiing is rather uncomfortable in pauses between a downhill run and the next one or whenever one has to move without wearing skis on one""s feet, since some difficulty in walking is observed.
U.S. Pat. No. 5,553,400 discloses a ski boot of the overlapping-flap type having a sole, an overlying body which is open at the front, and an open region, located at the foot instep, in which there are two pressure distribution plates arranged on the outer surface of the frontally open body.
The two plates run from the region of the boot tip to beyond the open region, where they bend upward, and are associated at the open region of the foot instep so that they can perform a longitudinal translatory motion with respect to the frontally open body and move transversely to the axis of the boot. They can also overlap so as to close the open region and the frontally open body.
In the boot, at least one of said pressure distribution plates must be rotatably associated by virtue of at least one fixed hinge which is arranged laterally to the open region of the foot instep.
The fixed hinge thus allows the rotary motion of one plate away from the other plate, so as to facilitate the opening of the foot instep region and of the open body.
When the boot is opened, the plates perform an outward combined rotary and translatory motion, moving mutually apart and also diverging and lifting, in their motion, the two partly overlapping flaps of the boot.
The main drawback of this conventional type of ski boot is the fact that user must apply, while inserting the foot, a force which is proportional to the opening of the flaps and is required in order to overcome the friction between the various surfaces involved.
Another drawback is the fact that some ski boots are constituted by a shell which is structurally weak because it is constituted by many mutually interacting parts.
For the same reason, the cost of manufacturing the shell is high because the shell is structurally complex.
The aim of the present invention is therefore to solve the noted technical problems, eliminating the drawbacks of the cited prior art, by providing a ski boot shell which increases the passage space for foot insertion and extraction so as to allow easy entries and exits of the foot with respect to the ski boot.
An important object is to provide a ski boot shell which achieves the intended aim without increasing the user""s insertion effort.
Another important object is to provide a ski boot shell which allows to use a small number of plates, thus reducing manufacturing costs and increasing the structural strength of the entire shell.
Another object is to provide a ski boot shell which improves the wraparound effect on the foot in the boot.
Another object is to provide a ski boot shell which is structurally simple and has low manufacturing costs.
This aim and these and other objects which will become better apparent hereinafter are achieved by a shell, particularly for a ski boot comprising a main body which is open in an upward region, characterized in that it comprises, at the foot instep region, two partially overlapping plate portions, each of said plate portions being rotatably pivoted to said shell by means of first rotary connection means arranged laterally to said shell on an axis which is approximately parallel to the resting plane of said sole, the rotation of said two plate portions being limited by second guided connection means arranged in the region in front of the heel.